Lon proxy point type selection

When you add a Lon proxy point, a default Niagara point type is pre-selected. Often, the data type (category) is either numeric or enum, and less often, boolean or string. A Lon proxy point supports default conversion between data types. This means when creating a proxy point, you can select another data type, if useful in your station’s application.

For example, if adding a proxy point for an nvo implemented with SNVT_Switch, and you are interested only in the “state” element as either false (Off) or true (On), and do not anticipate a “null” value, you can select a BooleanPoint instead of the pre-selected EnumPoint (Figure 52).

Figure 52. Changing point type when adding Lon proxy point

This would allow you to link the Out of the proxy BooleanPoint directly into a Logic-type kitControl object, without using an intermediate “conversion” object (StatusEnumToStatusBoolean). The proxy point would convert enum ordinals “0” to false, and “1” to true.

See Table 3 for how default Lon proxy point conversions are handled between data types.

Table 3. LonData element type to proxy point data type, default conversions

LonData element type	Proxy point type	Conversion method	Setup notes
Numeric	Boolean	False = 0, True = 1 value <=0 = False, >0 = True	—
	String	Convert between string representation and numeric values	—
	Enum	Numeric is enum ordinal	Add facet EnumRange
Boolean	String	True = “true”, False = “false”	—
Boolean	Numeric	False = 0, True = 1 value <=0 = False, >0 = True	—
Enum	Numeric	Numeric is enum ordinal	—
	Boolean	True to ordinal 1, false to ordinal 0.	—
	String	Read/Write enum tag	—
String	Numeric	Convert between string representation and numeric values	—
	Enum	String is enum tag	Add facet EnumRange
	Boolean	True = “true”, False = “false”	—

Also, when you add a proxy point under a Lon device for an nvi, nci, or cp, the Add dialog defaults to a writable type, for example NumericWritable or EnumWritable. Before creating the proxy point, you may wish to change to a read-only point type (if you wish to monitor only).